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This paper deals with the interaction forces between robotic foot and the soft terrain, in conjunction with the Terzaghi theory. To date, some basic assumptions and conclusions for Terzaghi theory are analyzed. Terzaghi is recognized as a popular option to predict the bearing capacity of the terrain with upper structures. In this paper, static models in Terzaghi theory and its extended versions are...
A real-time soil parameter estimation method for wheel motion control of a planetary rover is proposed. In this method, dominant soil parameters are updated in real time to compensate the error of the other parameters that are fixed by empirical typical values. Sinkage exponent and internal friction angle are the dominant characteristic parameters of wheel-soil interaction, because they dominate the...
Wheeled exploration robots are prone to slip during locomotion on deformable rough planetary terrain, which leads to loss of velocity and extra consumption of energy. Experimental results show that the power required for driving a wheel is an increasing function of its slip ratio; further, the tractive efficiency decreases rapidly after it reaches a peak value when the slip ratio is between 0.05 and...
Experimental investigation of planetary rovers' behavior requires low gravity (LG) simulation. It is true because rovers may have insufficient power to move and sink much deeper into soft soil in 1-g gravity environment. Constant-tension suspension is considered the best possible way for gravity compensation (GC) of rovers. Constant-tension cable has to be kept vertical, so tension generator mounts...
Numerical simulation analysis of the motion of wheeled mobile robots is significant for both their R&D and control phases, especially due to the recent increase in the number of planetary exploration missions. Using the position/orientation of the rover body and all the joint angles as generalized coordinates, the Jacobian matrices and recursive dynamic models are derived. Terramechanics models...
The wheel slip ratio is an important state variable in terramechanics research and the control of planetary rovers. Definitions of the slip ratio for a wheel with lugs and methods of estimating it for all wheels onboard have seldom been attempted. This paper presents several definitions for the slip ratio of a lugged wheel, which can be interconverted by altering the shearing radius. Equations for...
Identifying planetary soil parameters is not only an important scientific goal, but also necessary for exploration rover to optimize its control strategy and realize high-fidelity simulation. An improved wheel-soil interaction mechanics model is introduced, and it is then simplified by linearizing the normal stress and shearing stress to derive closed-form analytical equations. Eight unknown soil...
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